U.S. patent application number 12/167417 was filed with the patent office on 2010-01-07 for magnetic guided ablation catheter.
Invention is credited to Kirk Kochin Wu, Yongxing Zhang.
Application Number | 20100004632 12/167417 |
Document ID | / |
Family ID | 41464929 |
Filed Date | 2010-01-07 |
United States Patent
Application |
20100004632 |
Kind Code |
A1 |
Wu; Kirk Kochin ; et
al. |
January 7, 2010 |
MAGNETIC GUIDED ABLATION CATHETER
Abstract
Magnetic guided ablation catheters and methods of manufacture
are disclosed. In an exemplary embodiment, a catheter includes a
unitary flexible tubing having a proximal end and a distal end. A
plurality of magnets are positioned along an axis of the unitary
flexible tubing, the plurality of magnets provided within the
unitary flexible tubing. During operation, the plurality of magnets
are responsive to an external magnetic field to selectively
position and guide the catheter within a body of a patient.
Inventors: |
Wu; Kirk Kochin; (Walnut,
CA) ; Zhang; Yongxing; (Irvine, CA) |
Correspondence
Address: |
SJM/AFD - TRENNER;Legal Department
One St. Jude Medical Drive
St. Paul
MN
55117-9913
US
|
Family ID: |
41464929 |
Appl. No.: |
12/167417 |
Filed: |
July 3, 2008 |
Current U.S.
Class: |
604/528 |
Current CPC
Class: |
A61M 25/0009 20130101;
Y10T 29/49174 20150115; A61B 2018/00577 20130101; A61M 25/0127
20130101; A61B 2018/00357 20130101; A61B 18/1492 20130101; A61B
2017/00526 20130101 |
Class at
Publication: |
604/528 |
International
Class: |
A61M 25/01 20060101
A61M025/01 |
Claims
1. A catheter comprising: a unitary flexible tubing having a
proximal end and a distal end; a plurality of magnets positioned
along an axis of the unitary flexible tubing, the plurality of
magnets provided within the unitary flexible tubing; and wherein
the plurality of magnets are responsive to an external magnetic
field to selectively position and guide the catheter within a body
of a patient.
2. The catheter of claim 1, wherein the plurality of magnets are
pushed into the unitary flexible tubing.
3. The catheter of claim 1, wherein the plurality of magnets are
pushed into the unitary flexible tubing using a lubricant.
4. The catheter of claim 1, wherein the unitary flexible tubing is
lubricated with alcohol to facilitate receiving the plurality of
magnets therein.
5. The catheter of claim 1, further comprising an interference fit
between the plurality of magnets and the unitary flexible
tubing.
6. The catheter of claim 5, wherein the interference fit is formed
by an outer diameter of the plurality of magnets being larger than
an inner diameter of the unitary flexible tubing.
7. The catheter of claim 6, wherein the interference fit is formed
by an outer diameter of the plurality of magnets being about 0.005
inches larger than an inner diameter of the unitary flexible
tubing.
8. The catheter of claim 1, wherein the unitary flexible tubing is
heat-shrunk over the plurality of magnets.
9. The catheter of claim 1, wherein the unitary flexible tubing has
different flexibilities along a length the unitary flexible
tubing.
10. The catheter of claim 1, wherein the unitary flexible tubing is
more flexible toward the distal end and less flexible toward the
proximal end.
11. The catheter of claim 1, wherein the unitary flexible tubing
includes a plurality of segments, each segment having different
flexibility.
12. The catheter of claim 1, wherein the unitary flexible tubing
includes abrupt steps of flexibility between a plurality of
segments, the abrupt steps between segments defining locations for
providing magnets in the unitary flexible tubing.
13. The catheter of claim 1, wherein the unitary flexible tubing is
manufactured with different material properties to provide less
flexibility toward the proximal end and more flexibility toward the
distal end.
14. The catheter of claim 1, wherein the unitary flexible tubing is
formed thicker to provide less flexibility toward the proximal end,
and the unitary flexible tubing is formed thinner to provide more
flexibility toward the distal end.
15. The catheter of claim 1, further comprising an electrode
assembly at the distal end of the unitary flexible tubing, the
electrode assembly comprising a distal magnet.
16. The catheter of claim 1, wherein the plurality of magnets
comprise a first magnet, a second magnet, and a third magnet, the
third magnet spaced from the second magnet which is spaced from the
first magnet along the axis of the unitary flexible tubing, wherein
the magnets are responsive to an external magnetic field to
selectively position and guide the electrode assembly within a body
of a patient, wherein the second magnet is spaced from the first
magnet by a first distance along the axis of the unitary flexible
tubing, and the third magnet is spaced a second distance from the
second magnet along the axis of the tubing, wherein the second
distance is greater than the first distance.
17. A catheter comprising: a variably-flexible tubing having a
proximal end and a distal end, the variably-flexible tubing
prefabricated to be unitary in construction; at least one magnet
separately provided from an electrode assembly and spaced from the
electrode assembly along an axis of the flexible tubing; and
wherein the at least one magnet is responsive to an external
magnetic field to selectively position and guide the electrode
assembly within a body of a patient.
18. The catheter of claim 17, wherein the at least one magnet is
pushed into the variably-flexible tubing using a lubricant.
19. The catheter of claim 17, wherein the variably-flexible tubing
is heat-shrunk over the at least one magnet.
20. The catheter of claim 17, wherein an interference fit is formed
between the at least one magnet and the variably-flexible
tubing.
21. The catheter of claim 17, wherein the variably-flexible tubing
is more flexible toward the distal end and less flexible toward the
proximal end.
22. The catheter of claim 17, wherein the variably-flexible tubing
includes a plurality of different flexibility segments.
23. The catheter of claim 22, wherein the variably-flexible tubing
includes abrupt steps in flexibility between the different
segments, the abrupt steps between segments defining locations for
providing magnets in the unitary flexible tubing.
24. A catheter comprising: a unitary flexible tubing having a
proximal end and a distal end defining substantially an entire
length of the catheter; at least one magnet positioned along an
axis of the unitary flexible tubing, the at least one magnet
provided within the unitary flexible tubing; and wherein the at
least one magnet is responsive to an external magnetic field to
selectively position and guide the catheter within a body of a
patient.
25. The catheter of claim 24, wherein the at least one magnet is
pushed into the unitary flexible tubing using a lubricant.
26. The catheter of claim 24, wherein the unitary tubing is
heat-shrunk over the at least one magnet.
27. The catheter of claim 24, wherein an interference fit is formed
between the at least one magnet and the unitary tubing.
Description
BACKGROUND OF THE INVENTION
[0001] a. Field of the Invention
[0002] This invention relates generally to manufacturing of medical
instruments, and, more specifically, to the manufacture of a
navigable ablation catheter device positionable within a body of a
patient using an externally applied magnetic field.
[0003] b. Background Art
[0004] Catheters are flexible, tubular devices that are widely used
by physicians performing medical procedures to gain access into
interior regions of the body. Careful and precise positioning of
the catheters within the body is important to successfully
completing such medical procedures. This is particularly so when
catheters are used to produce emissions of energy within the body
during tissue ablation procedures. Conventionally, positioning of
such catheters was accomplished with mechanically steerable
devices. More recently, magnetically navigable catheter devices
have been developed that may be navigated with an externally
applied magnetic field. Such catheter devices can be complex in
their construction, and therefore are difficult to manufacture and
relatively expensive to produce.
[0005] Magnetic stereotactic systems have been developed that are
particularly advantageous for positioning of catheters, as well as
other devices, into areas of the body that were previously
inaccessible. Such systems utilize computer controlled
superconducting coils to generate specific magnetic fields or
gradients to move a catheter that is provided with magnetic
components responsive to such magnetic fields. The magnetic fields
and gradients are generated to precisely control the position of
the catheter within the patient's body. Once correctly positioned,
physicians may operate the catheter, for example, to ablate tissue
to clear a passage in the body. Specifically, such stereotactic
systems monitor the position of a tip of the catheter in response
to the applied magnetic fields of the superconducting coils. The
catheter tip may be guided to and positioned in a desired location
within the patient's body using well established feedback and
control algorithms.
[0006] Manufacture of magnetic-guided catheters can be challenging
and time consuming because the catheter shaft has to be fused
together to accommodate the magnets. The fusion process must be
precisely controlled, including parameters such as temperature,
time, side load, and tubing selection, in order to ensure
mechanical strength and cosmetic appearance. Therefore,
improvements in the manufacture of catheters utilized with magnetic
guidance and control systems, such as stereotactic systems, are
desired. Specifically, a low cost, yet high performance
magnetically guided ablation catheter is desirable which can be
manufactured without having to fuse the shaft.
BRIEF SUMMARY OF THE INVENTION
[0007] In various embodiments, magnetic guided catheters are
disclosed that are manufacturable at relatively low cost while
providing high performance for use with, for example, magnetic
stereotactic systems.
[0008] In one embodiment, the catheter may comprise: a unitary
flexible tubing having a proximal end and a distal end; and a
plurality of magnets positioned along an axis of the unitary
flexible tubing, the plurality of magnets provided within the
unitary flexible tubing. The plurality of magnets are responsive to
an external magnetic field to selectively position and guide the
catheter within a body of a patient.
[0009] In another embodiment, the catheter may comprise: a
variably-flexible tubing having a proximal end and a distal end,
the variably-flexible tubing prefabricated to be unitary in
construction; and at least one magnet separately provided from an
electrode assembly and spaced from the electrode assembly along an
axis of the flexible tubing. The at least one magnet is responsive
to an external magnetic field to selectively position and guide the
electrode assembly within a body of a patient.
[0010] In yet another embodiment, a catheter may comprise: a
unitary flexible tubing having a proximal end and a distal end
defining substantially an entire length of the catheter; and at
least one magnet positioned along an axis of the unitary flexible
tubing, the at least one magnet provided within the unitary
flexible tubing. The at least one magnet is responsive to an
external magnetic field to selectively position and guide the
catheter within a body of a patient.
[0011] Optionally, the magnet is pushed into the unitary flexible
tubing. For example, the magnet may be positioned on a mandrel and
pushed into the unitary flexible tubing using a lubricant such as,
alcohol, to facilitate receiving at least one magnet therein.
Alternatively, the unitary flexible tubing is heat-shrunk over the
at least one magnet. There may exist an interference fit between
the at least one magnet and the unitary flexible tubing. The
interference fit may be formed by an outer diameter of the at least
one magnet being larger than an inner diameter of the unitary
flexible tubing. For example, the interference fit may be formed by
an outer diameter of the at least one magnet being about 0.005
inches larger than an inner diameter of the unitary flexible
tubing.
[0012] Also optionally, the unitary flexible tubing may have
different flexibilities along a length the unitary flexible tubing.
In exemplary embodiments, the unitary flexible tubing is more
flexible toward the distal end and less flexible toward the
proximal end. For example, the unitary flexible tubing may be
manufactured with different material properties to provide less
flexibility toward the proximal end and more flexibility toward the
distal end. Or for example, the unitary flexible tubing may be
formed thicker to provide less flexibility toward the proximal end,
and the unitary flexible tubing is formed thinner to provide more
flexibility toward the distal end. The unitary flexible tubing may
include a plurality of segments, each segment having different
flexibility. The unitary flexible tubing may include abrupt steps
of flexibility between the segments, the abrupt steps defining
locations for providing magnets in the unitary flexible tubing.
[0013] The catheter may also comprise at least a second magnet, the
second magnet spaced from the at least one magnet along the axis of
the unitary flexible tubing. The catheter may also comprise at
least a third magnet, the third magnet spaced from the second
magnet along the axis of the unitary flexible tubing. The second
magnet may be spaced from the at least one magnet by a first
distance along the axis of the unitary flexible tubing, and the
third magnet may be spaced a second distance from the second magnet
along the axis of the tubing, wherein the third distance is greater
than the second distance. The magnets may have one of a cylindrical
shape and an ellipsoidal shape.
[0014] The catheter may be configured as at least one of a cardiac
ablation catheter, a cardiac electrophysiological mapping catheter,
and a cardiac diagnostic pacing stimuli catheter. Accordingly, the
catheter may further comprise an electrode assembly at the distal
end of the unitary flexible tubing, the electrode assembly
comprising a tip electrode and a band electrode. The electrode may
be configured as a radiofrequency ablation tip. The electrode
assembly may comprise a temperature sensor.
[0015] Still other features and method of manufacturing of magnetic
guided catheters are disclosed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 illustrates a first exemplary magnetic guided
catheter.
[0017] FIG. 2 is a magnified view of a distal end portion of the
catheter shown in FIG. 1.
[0018] FIG. 3 is a cross sectional view of the distal end portion
shown in FIG. 2.
[0019] FIG. 4 illustrates an exemplary manufacture process for the
magnetic guided catheter.
[0020] FIG. 5 illustrates a second exemplary embodiment of a
magnetic guide catheter.
[0021] FIG. 6 illustrates a magnet assembly for the catheter shown
in FIG. 4.
[0022] FIG. 7 illustrates the catheter shown in FIG. 4 in a first
operating position.
[0023] FIG. 8 illustrates the catheter shown in FIG. 4 in a second
operating position.
DETAILED DESCRIPTION OF THE INVENTION
[0024] FIG. 1 illustrates a first exemplary non-steerable,
single-use magnetic guided catheter 100 generally including a
flexible tubing 102, a tip assembly 104, positioning magnets 106
and 108 separately provided from and spaced from the tip assembly
104, a Y connector 110, a luer device 112, and an electrical
connector 114. The electrical connector 114 establishes electrical
connection with a power source (not shown) that operates electrodes
of the tip assembly 104 to perform, for example, ablation
procedures, mapping or pacing procedures, or to perform other
aspects of a medical procedure.
[0025] Although it will become evident that aspects of the
exemplary catheter 100 are applicable to a variety of medical
procedures and end uses, the invention will be described
principally in the context of a specific example of a magnetic
guided catheter. Specifically, the catheter 100 as shown in FIG. 1
is believed to be particularly advantageous as an ablation catheter
for creating endocardial lesions during cardiac ablation procedures
to treat arrhythmias, and also for cardiac electrophysiological
mapping and delivering diagnostic pacing stimuli. However, the
invention and the appended claims are not intended to be limited to
any specific example, including but not limited to specific
examples or embodiments described herein, except when explicitly
defined as such in the appended claims.
[0026] The Y-connector 110 separates a fluid tube 134 from
electrical lead wires extending between the tip assembly 104 and
the electrical connector 114. That is, the fluid tube 134 and the
lead wires forward of the Y-connector 110 pass internally through
the tubing 102, while aft of the Y-connector 110, the fluid tube
134 and the wire leads are exposed and separated for connection to
a fluid source (not shown) and a power source, respectively. The
electrical connector 114 may be a known connector that may be
engaged to a power source or power supply with, for example,
plug-in connection. One suitable electrical connector is a 14 pin
REDEL.RTM. plastic connector commercially available from LEMO of
Rohnert Park, Calif., although other connectors from various
manufacturers may likewise be utilized.
[0027] The luer device 112 in the depicted embodiment, as known in
the art, may be used to open or close a flow path so that fluid may
be passed through the Y-connector 110 and the tubing 102 to the tip
assembly 104 for irrigation purposes. The luer device 112 may be
considered optional for certain procedures.
[0028] The flexible tubing 102 includes a proximal end 116 coupled
to the Y-connector 110, a distal end 118 coupled to the tip
assembly 104, and an axial length extending between the proximal
and distal ends 116 and 118. In general, the flexible tubing 102
may be fabricated according to known processes, such as extrusion
processes. The tubing 102 may be fabricated from any suitable
tubing material known in the art of medical instruments, such as
engineered nylon resins and plastics, including but not limited to
PEBAX.RTM. tubing of Ato Fina Chemicals, France.
[0029] In an exemplary embodiment, the tubing 102 includes a first
portion 120 of the tubing 102 between the Y connector and the
magnet 108, a second portion 122 of the tubing 102 between the
magnet 106 and 108, and a third portion 124 of the tubing 102
extending between the magnet 106 and the tip assembly 104. In an
exemplary embodiment, the first portion 120, the second portion 122
and/or the third portion 124 may be fabricated from different
materials, grades of materials, and/or thicknesses of materials for
enhanced performance and flexibility of the tubing 102 in use of
the catheter assembly 100, as will be explained in more detail
below. It is noted, however, that although the tubing 102 may have
different portions or "zones", the tubing 102 is manufactured as a
unitary piece.
[0030] For example, in one embodiment, the first portion 120 of the
tubing 102 may include, for example a braided material that is
comparatively rigid and kink resistant. The first portion 120 may
be formed with different portions of braided material, semi-soft
material, and soft material fused to one another so that the first
portion 120 becomes increasingly flexible along the axial length as
the tube portion 120 approaches the magnet 108. The second portion
122 of the tubing 102 and the third portion 124 may include a soft
and flexible material having approximately equal flexible
properties. In the illustrated embodiment, each of the tubing
portions 120, 122 and 124 between the tip 104 and the magnets 106
and 108 share a common outside diameter of, for example, 7 French,
although in other embodiments, the tubing portions 120, 122 and 124
may be another size.
[0031] Additionally, and as shown in FIG. 1, the first portion 120
extends for the vast majority of the axial length of the tubing 102
between the proximal and distal ends 116 and 118. The second
portion 122 of the tubing 102 extends for a much shorter length
than the first portion 120, and the third portion 124 of the tubing
extends for a length that is shorter than the second portion 122.
By way of example only, in a specific embodiment the first portion
120 extends for an axial length of about 126.3 cm, the second
portion 122 extends for an axial length of about 2.2 cm, and the
third portion 124 extends for an axial length of about 0.8 cm,
although other relative lengths of the tube portions may likewise
be employed in other embodiments. The different relative lengths of
the tube portions 120, 122 and 124, as well as the different
flexible properties of the tube portions 120, 122 and 124, allows
the tip assembly 104 to be more precisely positioned within a
patient's body, while also avoiding problems of kinks and excessive
deflection of the tubing 102 along the majority of its length
during use and handling.
[0032] As another consequence of the tubing portions 122 and 124
having an unequal length, the magnet 106 is a spaced a first
distance from the tip assembly 104, and the magnet 108 is spaced a
second and farther distance from the magnet 106 via the tubing
portion 122 being longer than the tubing portion 124. Due to the
spacing of the magnets 106 and 108 relative to one another and also
to the tip assembly 104, which as explained below also includes a
positioning magnet, the spacing of the magnets permits adjustment
in positioning of the tip assembly 104 in response to variation in
an externally applied magnetic field that may otherwise be
difficult, if not impossible, if the magnets were provided in an
equal or uniform spaced relation to one another. It is
contemplated, however, that in another embodiment the tip 104, the
magnet 106 and the magnet 108 could be equally spaced from one
another if desired.
[0033] In operation, the distal end of the catheter 100 including
the tip 104 is navigated to the site in the body where a medical
procedure, such as an atrial mapping, pacing and ablation are to
occur. The distal end may extend, for example, into a heart chamber
of a patient. Once the distal end is in the chamber, a magnetic
field is applied to provide an orienting force to the distal end,
causing the magnets to respond to the applied magnetic field and
flex the tubing portions 124 and 122 to precisely position the tip
104 for performance of the procedure at a specific location. The
magnetic fields used to orient the tip 104 may be generated with,
for example, a magnetic stereotactic system 126. Such stereotactic
systems are known and are commercially available from, for example,
Stereotaxis of St. Louis, Mo. Such systems may include movable
source magnets outside the body of the patient, and operative
details of such systems are disclosed in, for example, U.S. Pat.
Nos. 6,475,223 and 6,755,816, the disclosures of which are hereby
incorporated by reference in their entirety. While the catheter 100
is believed to be particularly advantageous for use with a
stereotactic system, it is contemplated that magnetic fields and
gradients to deflect the catheter tip 400 may alternatively be
generated by other systems and techniques if desired.
[0034] FIG. 2 is a magnified view of a distal end portion 130 of
the catheter 100 shown in FIG. 1. The tip assembly 104 may be
coupled to the tube portion 124 at one end and the magnets 106 and
108 are provided in the tube portion 124.
[0035] The tip electrode 140 may be an 8 Fr hemispherical-shaped
tip electrode that is, for example, 2 mm in length. The tip
electrode 140 is formed with a plurality of open conduits that form
the irrigation ports for saline irrigation. The tip electrode 140
may be fabricated from 90% platinum and 10% iridium, or other
materials known in the art. The tip electrode 140 may be visually
recognizable under fluoroscopic exposure. While formed as an
integral unit, the tip electrode 140 may include multiple electrode
elements, such as ring electrodes for electrophysiological mapping
purposes, spaced from one another by dielectric materials as is
known in the art.
[0036] The tip assembly 104 is particularly suited for ablation
procedures wherein the electrodes 140 are energized to deliver
radio frequency waves at the site of an abnormal pathway in the
body. Radiofrequency (RF) energy may therefore be coupled to
biological tissue surrounding the catheter tip. Ablation procedures
are typically used, for example, within the interior chambers of
the heart to thermally ablate cardiac tissue. The electrodes 140
may additionally be operated to record intracardiac signals and to
provide pacing signals.
[0037] FIG. 3 is a cross sectional view of the distal end portion
130 wherein an inner tube 133 defining a central lumen 134 extends
through each tube portion 120, 122, and 124, and also through
central bores formed in the magnets 106 and 108. The inner tube 133
is smaller in diameter than the tubing 102 and its portions 120,
122 and 124, such that the tube 133 passes through a portion of the
internal opening of the tubing 102, while leaving room to spare.
Thus, internal areas of the tubing 102 that are not occupied by the
lumen may be used to accommodate lead wires for electrical
components of the tip assembly 104.
[0038] The tip assembly 104 may also include a positioning magnet
136, with the tube 133 and lumen 134 also passing through a central
bore in the magnet 136. The lumen 134 is in fluid communication
with the luer 112 (FIG. 1) on one end and with the irrigation ports
132 of the tip assembly 104 at the other. Thus, an irrigation
fluid, such as saline, may be injected through the distal end
portion 130. The tube 133 may be, for example, a braided polyimide
tube that maintains the flow path through the lumen 134 in all
orientations of the tip assembly 104, without compromising the
flexibility of the tubing 102.
[0039] The magnets 106 and 108 are each permanent magnets formed
from, for example, neodymium-iron boron--45 (NdFeB-45) into an
elongated cylindrical shape. The magnets 106 and 108 may comprise
flexible magnets. The flexible magnets may be stacked, flexible
magnetic elements, or made of flexible magnet strips, or extruded
flexible magnets in a tubular form. Alternatively, the magnets 106
and 108 may be formed from other materials and may have different
shapes.
[0040] In an exemplary embodiment, the magnets 106 and 108 are
generally cylindrical shaped permanent magnets. A central bore may
extend through the magnets 106 and 108 so that tubing and/or wiring
can extend through the bore in the magnet and pass centrally
through the magnets 106 and 108. Alternatively, or in addition to,
the magnets 106 and 108 may be formed with a recess on the outer
exterior that allows the lead wires to pass around the outer
surface of the magnets 106 and 108.
[0041] The magnets 106 and 108 may be installed within tubing 102
in such a manner so that the tubing remains unitary in
construction. Accordingly, the catheter can be manufactured without
requiring magnet-shaft fusion, and thus there are no joints,
ensuring high reliability and safety of the catheter. In comparison
with the magnet-shaft fusion assembly procedures noted in the prior
art, the unitary tubing is easier to manufacture, takes less time
to manufacture, and does not require a fusion machine, which tend
to be expensive and may require validation and qualification prior
to use. In addition, undesirable stiffness is avoided because the
junctions between the magnet and the shaft are eliminated.
[0042] FIG. 4 illustrates an exemplary manufacture process for the
magnetic guided catheter. In an exemplary embodiment, the magnets
106 and 108 may be pushed into the tubing during the manufacture
process in the direction illustrated by arrow 103. For example, the
magnets 106 and 108 may be positioned on mandrels 101 and 105,
respectively, and pushed into the tubing 102 one at a time using a
lubricant such as, alcohol, to facilitate receiving the magnets 106
and 108 therein. The alcohol conveniently evaporates after a short
time. The magnets 106 and 108 are shown mounted on the mandrels 101
and 105 outside of the tubing 102. The magnets 106 and 108 are
inserted into the tubing 102 one at a time, by pushing the mandrels
101 and 105 separately and sequentially in the direction of arrow
103.
[0043] According to this method, there may exist an interference
fit between the magnets 106 and 108, and the tubing 102, thereby
securing the position of the magnets 106 and 108. It is noted that
the drawings are exaggerated to better illustrate the interference
fit. In reality, the interference fit may not be as pronounced as
it is shown in the drawings. The interference fit ma, be formed by
an outer diameter of the at least one magnet being larger than an
inner diameter of the unitary flexible tubing. For example, the
interference fit may be formed by the magnets 106 and 108 having an
outer diameter about 0.005 inches larger than the inner diameter of
the tubing 102.
[0044] In another exemplary embodiment, the magnets 106 and 108 may
be pushed into the tubing 102 without any interference fittings. In
this embodiment, the tubing 102 may be wrapped in heat-shrink film
or heat-shrink tubing. The heat-shrink process shrinks the
heat-shrink film or tubing around the tubing 102 so that the
position of magnets 106 and 108 is secured within the tubing
102.
[0045] Heat-shrink processes are well understood in the arts. For
purposes of discussion, however, the process may implement any of a
wide variety of commercially available heat shrink film or tubing.
The magnets 106 and 108 are first positioned within the heat shrink
tubing. The magnets are readily positioned while the heat shrink
tubing is in an initial state (e.g., at room temperature) prior to
processing. Optionally, the magnet may be pretreated with a
coating, e.g., to reduce the effects of corrosion. Application of
heat to the heat shrink film or tubing shrinks the film or tubing
around the magnets 106 and 108. Shrinkage of the tubing around the
magnet applies the necessary pressure to maintain the magnets 106
and 108 in the desired position within the tubing 102 after the
heat shrink film or tubing cools.
[0046] Also in exemplary embodiments, the catheter 100 can be
constructed to have different flexibilities along the length of
tubing 102, particularly in the distal region where the magnets are
placed. Typically, the portion 124 (FIG. 1) between the distal end
(where the tip electrode is located) and the first magnet 106 is
desired to be the most flexible. The portion 122 between the first
magnet 106 and the second magnet 108 disposed proximally from the
first magnet 106 is desired to have less flexibility. Still
additional portions and additional magnets may be provided, with
the proximal portions having less and less flexibility.
[0047] The flexibility can be determined by material properties
and/or thickness. Thus, the unitary tubing 102 can be made to have
varying material properties along its length toward the distal end,
so that the different portions will have different flexibilities.
The shaft can also decrease in thickness toward the distal end. A
thinner wall of the tubing 102 results in greater flexibility,
while a thicker wall of the tubing 102 results in less
flexibility.
[0048] Flexibility can change either continuously/gradually or in
abrupt steps between the segments. The abrupt steps may be useful
in defining the locations of the magnets, especially in the
embodiment where the magnets are pushed into the shaft with a
lubricant. As the magnets 106 and 108 pass through different
flexibility zones defined by abrupt steps, the abrupt change in
flexibility provides tactile feedback that the magnets 106 and 108
are passing from one flexibility zone to another.
[0049] FIG. 5 illustrates a second exemplary embodiment of a
magnetic guided catheter 200 that is similar in many aspects to the
catheter 100 described above. Like components and features of the
catheter 100 are indicated with like reference characters in FIG.
4. Unlike the catheter 100, the catheter 200 includes magnets 204
and 206 instead of the magnets 106 and 108.
[0050] FIG. 6 illustrates a magnet assembly for the catheter 200.
Unlike the magnets 106 and 108 that are cylindrical in shape and
have a constant outer diameter, the magnet 204 is outwardly flared
and is ellipsoidal in its counter and somewhat resembles a football
with truncated ends. That is, the outer diameter of the magnet 204
is largest at the axial midpoint of the magnet, with the outer
diameter decreasing from the midpoint to the opposing ends of the
magnet 204, providing the magnet 204 with a curved profile along
the axial length of the magnet 204.
[0051] The magnet 204 is encapsulated in the tube portions 124 and
122 in the manner described above. The tube 133 and the lumen 134
pass centrally through the magnet 204. The magnet may be formed
from, for example, neodymium-iron boron--45 (NdFeB-45) into the
illustrated shape or an alternative shape. The magnet 206 (FIG. 6)
may be formed in the same or different shape from the magnet
204.
[0052] FIG. 7 and FIG. 8 illustrate the catheter 200 in exemplary
first and second operating positions with the distal end including
the tip assembly 102 deflected to different positions with the
magnets 204 and 206. By applying magnetic fields to the magnets 204
and 206, and also the magnet 224 (FIG. 7) in the tip, the distal
end of the catheter 200 may be moved to desired positions within a
patient's body. The magnetic fields may be generated and controlled
by, for example, a magnetic stereotactic system 240. By virtue of
the positioning magnet in the tip and the external magnets 204 and
206, the tip may be precisely positioned at a specific location
within the patient's body.
[0053] The unitary construction of the flexible tubings of the
catheters 100 and 200 is believed to provide manufacturing
benefits, and also performance benefits, in relation to
conventional, and more complicated, catheter constructions for use
with stereotactic systems. The catheter can be manufactured without
requiring magnet-shaft fusion and without joints, ensuring high
reliability and safety of the catheter. The unitary tubing is
easier to manufacture, takes less time to manufacture, and does not
require an expensive and complicated fusion machine. Eliminating
the junction of the magnet and the shaft also reduces or altogether
eliminates undesirable stiffness. In addition, the magnets that are
separately provided from the electrode tips also reduces complexity
and parts count in the tip assembly relative to other known
catheter tips providing comparable functionality. The unitary
flexible tubing may extend along substantially the entire length of
the catheter body, and may have a distal end to be coupled to an
electrode assembly and a proximal end to be coupled to a handle.
Alternatively, the unitary flexible tubing may extend along a
portion of the catheter body with no fused connections between the
magnets, but may be attached to additional components to form the
entire length of the catheter body. For example, the unitary
flexible tubing containing the magnets with no fused connections
may be fused with another flexible tubing to form the entire length
of the catheter body.
[0054] While the invention has been described in terms of various
specific embodiments, those skilled in the art will recognize that
the invention can be practiced with modification within the spirit
and scope of the claims.
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